Monthly interpolated coral d18O records from Bonaire corals

Several proxy-based and modeling studies have investigated long-term changes in Caribbean climate during the Holocene, however, very little is known on its variability on short timescales. Here we reconstruct seasonality and interannual to multidecadal variability of sea surface hydrology of the southern Caribbean Sea by applying paired coral Sr/Ca and d18O measurements on fossil annually banded Diploria strigosa corals from Bonaire. This allows for better understanding of seasonal to multidecadal variability of the Caribbean hydrological cycle during the mid- to late Holocene. The monthly resolved coral Delta d18O records are used as a proxy for the oxygen isotopic composition of seawater (d18Osw) of the southern Caribbean Sea. Consistent with modern day conditions, annual d18Osw cycles reconstructed from three modern corals reveal that freshwater budget at the study site is influenced by both net precipitation and advection of tropical freshwater brought by wind-driven surface currents. In contrast, the annual d18Osw cycle reconstructed from a mid-Holocene coral indicates a sharp peak towards more negative values in summer, suggesting intense summer precipitation at 6 ka BP (before present). In line with this, our model simulations indicate that increased seasonality of the hydrological cycle at 6 ka BP results from enhanced precipitation in summertime. On interannual to multidecadal timescales, the systematic positive correlation observed between reconstructed sea surface temperature and salinity suggests that freshwater discharged from the Orinoco and Amazon rivers and transported into the Caribbean by wind-driven surface currents is a critical component influencing sea surface hydrology on these timescales.

Auschwitz e os limites da cultura : Anotações para uma sociologia crítica da educação

A proposta de apresentaçaoaponta para algumas anotaçoes sobre uma sociologia crítica da educaçao a partir do pensamento de Theodor W. Adorno. Desse modo, discutem-se aqui os limites da cultura na sociedade capitalista, sendo o episódio de Auschwitz a grande metáfora da própria cultura absorvida pela lógica de dominaçao. Para Adorno Auschwitz é o símbolo da consciência coisificada, transfigurada também no símbolo da modernidade e da civilizaçao. Auschwitz é a "barbárie sofisticada" ou civilizaçao que expoe sua barbárie, eis o paradoxo. O olhar de Adorno está voltado para a situaçao humana após esta catástrofe que nos direciona a uma crítica à civilizaçao. Sua afinidade com esse episódio, criado sob a mao humana, nasce a partir de uma exigência de ler a contrapelo a própria cultura.Nesse sentido pretende-sediscutir a condiçao da educaçao nos dias atuais, a partir de uma concepçao sociológica crítica, bem como seus desdobramentos. A questao que se coloca é: como compreender uma sociologia crítica da educaçao e as condiçoes de efetivá-la na perspectiva de se evitar Auschwitz no âmbito da sociedade contemporânea?

Electron spin resonance (ESR) and 14C dating in sediments of Bonaire, Leeward Antilles

The coastal deposits of Bonaire, Leeward Antilles, are among the most studied archives for extreme-wave events (EWEs) in the Caribbean. Here we present more than 400 electron spin resonance (ESR) and radiocarbon data on coarse-clast deposits from Bonaire's eastern and western coasts. The chronological data are compared to the occurrence and age of fine-grained extreme-wave deposits detected in lagoons and floodplains. Both approaches are aimed at the identification of EWEs, the differentiation between extraordinary storms and tsunamis, improving reconstructions of the coastal evolution, and establishing a geochronological framework for the events. Although the combination of different methods and archives contributes to a better understanding of the interplay of coastal and archive-related processes, insufficient separation, superimposition or burying of coarse-clast deposits and restricted dating accuracy limit the use of both fine-grained and coarse-clast geoarchives to unravel decadal- to centennial-scale events. At several locations, distinct landforms are attributed to different coastal flooding events interpreted to be of tsunamigenic origin. Coastal landforms on the western coast have significantly been influenced by (sub)-recent hurricanes, indicating that formation of the coarse-clast deposits on the eastern coast is likely to be related to past events of higher energy.

Auschwitz e os limites da cultura : Anotações para uma sociologia crítica da educação

A proposta de apresentaçaoaponta para algumas anotaçoes sobre uma sociologia crítica da educaçao a partir do pensamento de Theodor W. Adorno. Desse modo, discutem-se aqui os limites da cultura na sociedade capitalista, sendo o episódio de Auschwitz a grande metáfora da própria cultura absorvida pela lógica de dominaçao. Para Adorno Auschwitz é o símbolo da consciência coisificada, transfigurada também no símbolo da modernidade e da civilizaçao. Auschwitz é a "barbárie sofisticada" ou civilizaçao que expoe sua barbárie, eis o paradoxo. O olhar de Adorno está voltado para a situaçao humana após esta catástrofe que nos direciona a uma crítica à civilizaçao. Sua afinidade com esse episódio, criado sob a mao humana, nasce a partir de uma exigência de ler a contrapelo a própria cultura.Nesse sentido pretende-sediscutir a condiçao da educaçao nos dias atuais, a partir de uma concepçao sociológica crítica, bem como seus desdobramentos. A questao que se coloca é: como compreender uma sociologia crítica da educaçao e as condiçoes de efetivá-la na perspectiva de se evitar Auschwitz no âmbito da sociedade contemporânea?

Oxygen isotopes and Sr/Ca ratios of fossil corals from Bonaire

Explanations for the demise of the Classic Maya civilization on the Yucatán Peninsula during the Terminal Classic Period (TCP; CE 750-1050) are controversial. Multiyear droughts are one likely cause, but the role of the Caribbean Sea, the dominant moisture source for Mesoamerica, remains largely unknown. Here we present bimonthly resolved snapshots of reconstructed sea surface temperature (SST) and salinity (SSS) variability in the southern Caribbean from precisely dated fossil corals. Our fossil coral results from Bonaire indicate strong interannual to decadal SST and SSS variability in the southern Caribbean Sea during the TCP with multiyear extremes of high SSS and high SST that coincide with droughts on the Yucatán Peninsula. The results are best explained by changed Caribbean SST gradients affecting the Caribbean low-level atmospheric jet with consequences for Mesoamerican precipitation, possibly linked to changes in Atlantic Meridional Overturning Circulation strength. Our findings provide a new perspective on the anomalous hydrological changes on the Yucatán Peninsula during the TCP that complement the often-suggested southward displacement of the Intertropical Convergence Zone. We advocate for a strong role of ocean-atmosphere interactions in the Caribbean Sea related to the multiyear variations in Caribbean Sea surface conditions as an important driver of the spatially complex pattern of hydrological anomalies during the TCP.

40-year long monthly-resolved Sr/Ca record from 2.35 ka Bonaire coral, sample BON-6-A

We present a 40-year long monthly resolved Sr/Ca record from a fossil Diploria strigosa coral from Bonaire (Southern Caribbean Sea) dated with U/Th at 2.35 ka before present (BP). Secondary modifiers of this sea surface temperature (SST) proxy in annually-banded corals such as diagenetic alteration of the skeleton and skeletal growth-rate are investigated. Extensive diagenetic investigations reveal that this fossil coral skeleton is pristine which is further supported by clear annual cycles in the coral Sr/Ca record. No significant correlation between annual growth rate and Sr/Ca is observed, suggesting that the Sr/Ca record is not affected by coral growth. Therefore, we conclude that the observed interannual Sr/Ca variability was influenced by ambient SST variability. Spectral analysis of the annual mean Sr/Ca record reveals a dominant frequency centred at 6-7 years that is not associated with changes of the annual growth rate. The first monthly resolved coral Sr/Ca record from the Southern Caribbean Sea for preindustrial time suggests that fossil corals from Bonaire are suitable tools for reconstructing past SST variability. Coastal deposits on Bonaire provide abundant fossil D. strigosa colonies of Holocene age that can be accurately dated and used to reconstruct climate variability. Comparisons of long monthly resolved Sr/Ca records from multiple fossil corals will provide a mean to estimate seasonality and interannual to interdecadal SST variability of the Southern Caribbean Sea during the Holocene.